Particle Coarsening in ternary, multiphase -multicomponent, systems is quite different than its binary counterpart in that the presence of one phase can affect the coarsening behavior of another. We have shown by analytic analysis and numerical simulation that the interaction between two coexisting phases depends on: solution thermodynamics, diffusivities, and equilibrium concentration differences between matrix and precipitate phases. Therefore, different ternary systems create different cross phase interactions which affect coarsening behavior. For example, spatial correlations between the two coarsening phases are a strong function of this interaction and can lead to spatial ordering between the two phases. Also, specific ternary systems can produce kinetic instabilities and pattern formation.